The present embodiments relate to a method and system for providing fail-safe communication in a compromised network device, and in particular, for providing fail-safe communication in or over a compromised transformer isolated communication channel of a network device, such as often employed in a fire safety system.
Fire safety systems may include fire alarm control panels connected with or coupled to other fire alarm equipment, such as voice panels, terminals, and/or workstations, over or via a communication channel or network. A conventional communication channel or network typically includes a standard transformer isolated communication channel, such as employed in standard Ethernet communication networks where each node of a network has an Ethernet Transformer for each channel or port on the network. The Standard for Control Units and Accessories for Fire Alarm Systems (UL 864), which governs fire alarm safety systems, requires that each fire alarm safety system be configured to detect ground faults. A ground fault may be an unintentional short or insufficient impedance path to ground or earth. The ground fault may be caused by or due to moisture or condensation, corrosion, oxidation, and/or other physical or conduction damage to a circuit.
Some ground fault detection devices are known. For example, U.S. Patent Publication No. 2011/0025341 describes a method of externally testing a network device for a ground fault. Specifically, an external circuit may be connected to a port of a network device to detect a ground fault in that port. Such a method is, however, intrusive and potentially introduces undesirable electrical effects that reduce transmission length.